This invention relates to a correction method for ink jet printing that utilizes a continuous ink jet print head that employs multiple nozzles.
Ink jet printers are well known in the printing industry. Ink jet printers are just one of many different types of printing systems that have been developed which include laser electrophotographic printers, LED electrophotographic printers, dot matrix impact printers, thermal paper printers, film recorders, thermal wax printers and dye diffusion thermal transfer printers. Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing industry because of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfers and fixing. However, there is an ongoing demand for improved digitally-controlled printing systems that are able to produce high color images at a high speed and low cost using standard paper.
U.S. Pat. No. 4,346,387 discloses a continuous ink jet printer which utilizes electrostatic charging tunnels that are placed close to the point where ink droplets are being ejected in the form of a stream. Selected droplets are electrically charged by the charging tunnels. The charged droplets are deflected downstream by the presence of deflector plates that have a predetermined electric potential difference between them. A gutter may be used to intercept the charged droplets, while the uncharged droplets are free to strike the recording medium.
U.S. Pat. No. 6,079,821 disclosed a continuous ink jet printer which utilizes thermal energy to deflect the droplets. A heater section is employed to produce an asymmetric application of heat to an ink stream to control the direction of the stream between a print direction and a non-print direction.
While continuous ink jet printers enjoy the advantage of high printing speed and productivity, there is a problem with them due to malfulnctioning nozzles. For example, a print head is rarely manufactured perfectly, so that there is a small percentage of nozzles in a print head which are imperfect. In addition, a small percentage of nozzles may also become damaged during printing. Without correction, the malfunctioning nozzles on a print head may cause printing failures due to, for example, misdirected jets of ink.
It is an object of this invention to provide a method for correcting the performance of a multi-nozzle, continuous ink jet print head with a malfunctioning nozzle without affecting the performance of the other nozzles.
It is another object of this invention to selectively block a malfunctioning nozzle of an ink jet print head by a thermal triggering technique.
These and other objects are achieved in accordance with this invention comprising a method for correcting the performance a continuous ink jet print head having a nozzle plate with a plurality of nozzles each comprising an orifice, at least one of the nozzles being a malfunctioning nozzle, the method comprising:
a) determining which nozzle of the nozzle plate is malfunctioning;
b) applying a heat-activatable material over the surface of the nozzle plate;
c) applying heat to the malfunctioning nozzle, thereby causing the heat-activatable material to flow into the orifice of the malfunctioning nozzle to block it; and
d) removing any excess heat-activatable material.
By use of the invention, a malfunctioning nozzle can be blocked, without affecting the performance of the other nozzles, so that the print head can continue to be used. The printer can be programmed to use only the functional nozzles.